“What do you find dispositive of Peter’s founding of the Church at Antioch in Acts 11?”
He didn’t.
(Acts 11:19-21) “Now they which were scattered abroad upon the persecution that arose about Stephen travelled as far as Phenice, and Cyprus, and Antioch, preaching the word to none but unto the Jews only. And some of them were men of Cyprus and Cyrene, which, when they were come to Antioch, spake unto the Grecians, preaching the Lord Jesus. And the hand of the Lord was with them: and a great number believed, and turned unto the Lord.”
In that passage only men of Cyprus and Cyrene and Barnabas and Saul are mentioned later in the passage, as founding he church.
The point of the sentence is that those men spoke to the greeks, not founded the church.
There is nothing positively asserting anything about the founding of the Church at Antioch in this passage.
If you can't recognize that fact, you are not qualified to render an opinion.